Using an additive to fix a rear main seal leak

[DaveK22]

I have a very small oil leak. I brought to my local shop and the said it appears to be from the rear main seal. He said that the transmission would have to be dropped to fix....fairly expensive job

So, since it's a small leak...I was wondering about trying a rear main seal oil additive. The brand Bar's seems like it has 4/5 star reviews on Amazon & Advance Auto websites. Some say it worked great, others claim it did nothing.

Is there any harm in trying this? I mean for only $10 I would be willing to give it a try as long as doesn't "hurt" anything else.

 

[Jerry Bransford]

Personally I'd switch to a High Mileage version of a conventional 10W-30 engine oil. Especially if you're running a synthetic engine oil now which commonly causes RMS leaks. The High Mileage version is good at fixing RMS leaks, it fixed a major RMS leak my daily driver BMW developed in under a week. Some reviews I read on additives like that one from Bar's said it didn't help.

 

[DaveK22]

I noticed the leak after I used BG MOA additive along with conventional oil after hearing a mechanic on a local talk radio show raving over the product. I'm afraid that is what caused this as it never leaked before using that additive. I have since switched to just plain oil syn blend. I still see a small leak after that. Part of problem is I don't drive the jeep that much as it is not a daily driver & it's my summer "fun" vehicle.

I see another product called AT-205 with even better reviews. I'm leaning towards trying it even though most of these additives say it has to be driven for a while before it starts working.

 

[Kid Mechanic]

I noticed the leak after I used BG MOA additive …

Why did you use this mystery additive to begin with?

Just try what @Jerry Bransford always recommends and if it still leaks then try the magic cure all stuff before replacing the seal. Then you will know what works and what doesn’t.

 

[Gilaguy23]

What Jerry said is you best bet. We have a 04 4runner that has a bad O ring between the 4h/4l shift box. To fix it correctly the T/C needs to come out,get dissasembled and a C clip removed to to pull the shift box and replace a $1 O ring. I mixed up a bit of 80/90 with some Blue devil rm stop leak and it stopped the leak for now. Id guess any sela engine or elsewhere will eventually die from using this crap, but for now...what the heck.

 

[Jerry Bransford]

I have since switched to just plain oil syn blend. I still see a small leak after that.

Try changing to a pure conventional High Mileage 10W-30, my bet is it'll cure that leak.

 

[Artsifrtsi]

I use the high mileage oil in my TJ, and the underside stays dry.

 

[WestCoastDan]

That additive stuff did nothing to slow the leak from our RMS or my wallet.

 

[WestCoastDan]

I have a very small oil leak. I brought to my local shop and the said it appears to be from the rear main seal. He said that the transmission would have to be dropped to fix....fairly expensive job

So, since it's a small leak...I was wondering about trying a rear main seal oil additive. The brand Bar's seems like it has 4/5 star reviews on Amazon & Advance Auto websites. Some say it worked great, others claim it did nothing.

Is there any harm in trying this? I mean for only $10 I would be willing to give it a try as long as doesn't "hurt" anything else.

View attachment 289654

Aside from giving this a try, seek a different mechanic as well, because the trans does not have to be removed to fix the RSM on a Jeep (assuming you have the 4.0L engine, I don't know about the 2.5L).

 

[Jerry Bransford]

Aside from giving this a try, seek a different mechanic as well, because the trans does not have to be removed to fix the RSM on a Jeep (assuming you have the 4.0L engine, I don't know about the 2.5L).

True, the 4.0 uses a 2-piece rear main seal. The 2.5 uses a 1-piece seal requiring the transmission be dropped. But OP do try switching to a high mileage conventional engine oil first.

 

[machoheadgames]

High mileage conventional might fix it. If not, definitely consult another mechanic regarding the RMS replacement. 4.0 is 2 piece and needs oil pan dropped, 2.5 is 1 piece and needs transmission pulled.

 

[nathanotis]

BG makes good products. My shop uses them and they work (Standard disclaimers apply, I'm not sponsored, etc). Among other things, BG's MOA is a detergent. It probably got rid of some gunk that was plugging up leaky spots.

Go for the 10w30 High Mileage option. If that doesn't help (or stop) the leak, then consider more drastic things.

I'm always leery of products that claim to plug holes just by dumping them in... How can they tell bad holes from good ones?

 

[Jerry Bransford]

I'm always leery of products that claim to plug holes just by dumping them in... How can they tell bad holes from good ones?

X2 exactly.

 

[Artsifrtsi]

... How can they tell bad holes from good ones?

Sums up a lot of exes...

 

[DaveK22]

Try changing to a pure conventional High Mileage 10W-30, my bet is it'll cure that leak.

Jerry-
Even though I just changed my oil (NAPA Motor Oil 5W30 Synthetic Blend ) like only 50 miles ago, I guess I can always do another change & try the conventional high mileage like you suggested.

Also, good info on the 4.0L not needing the tranny dropped.

 

[Jerry Bransford]

Jerry-
Even though I just changed my oil (NAPA Motor Oil 5W30 Synthetic Blend ) like only 50 miles ago, I guess I can always do another change & try the conventional high mileage like you suggested.

Same thing with me, it hadn't been long since changing the oil in my BMW that I decided to switch to a High Mileage conventional. Fortunately it fixed the big RMS leak it had developed.

 

[Fishtaco]

Jerry-
Even though I just changed my oil (NAPA Motor Oil 5W30 Synthetic Blend ) like only 50 miles ago, I guess I can always do another change & try the conventional high mileage like you suggested.

Also, good info on the 4.0L not needing the tranny dropped.

I changed to a synth blend last change and got a minor RMS leak but it doesn't bother me as its pretty minor, there was no leak with the conventional that came out but it seems to run a bit quieter on the Magnatec 10w-40 I used,

Personally I would use Blue Devil RMS leak and drive it in, what have you got to loose? you have new oil in it already and if the Blue Devil doesn't work then change to Conventional.

 

[Fishtaco]

BG makes good products. My shop uses them and they work (Standard disclaimers apply, I'm not sponsored, etc). Among other things, BG's MOA is a detergent. It probably got rid of some gunk that was plugging up leaky spots.

Go for the 10w30 High Mileage option. If that doesn't help (or stop) the leak, then consider more drastic things.

I'm always leery of products that claim to plug holes just by dumping them in... How can they tell bad holes from good ones?

Isn't RMS leak additive just a seal lubricant and not a hole filler?

 

[Artsifrtsi]

I changed to a synth blend last change and got a minor RMS leak but it doesn't bother me as its pretty minor, there was no leak with the conventional that came out but it seems to run a bit quieter on the Magnatec 10w-40 I used,

Personally I would use Blue Devil RMS leak and drive it in, what have you got to loose? you have new oil in it already and if the Blue Devil doesn't work then change to Conventional.

Only time to add a stop leak is right before you plan to sell the vehicle. Some are seal conditioners, and soften the rubber, some are a thick goo that may or may not blend with the oil, and seek out any small hole to fill... passageways included.

High mileage oil is designed to keep the seals conditioned and working smoothly. I will continue to use high mileage in my jeep, we have had the Jeep since delivery in 2005 (new with 8 miles on the clock) and plan to pass it on to our 8 year old. Have been using the high mileage oil since 100k miles, and other than the rear pinion seal finally giving out this summer (130k miles) the Jeep doesn't drip a drop of oil.

 

[nathanotis]

Isn't RMS leak additive just a seal lubricant and not a hole filler?

Probably? I don't know the product. That said, I was thinking more of the myriad "stop-leak" products on the market for our vehicles (head gasket, radiator, etc). Indiscriminate filling of holes stops fluid flow in SOME places it's supposed to flow. At best, they're Band-Aids.